C# 当使用C首次加载页面时，Dropbox的第一项不工作#

加载页面时，Dropbox的第一项不起作用，但如果在Dropbox中选择第二项，表单将填充相关数据。如果我回到之前选择的第一个项目，它将在这次工作。请帮忙。谢谢

HTML代码

<asp:DropDownList ID="DropDownListUpdateSample" runat="server" Height="37px" Width="132px" CssClass="auto-style111" AutoPostBack = "true" OnSelectedIndexChanged="DropDownListUpdateSample_SelectedIndexChanged" AppendDataBoundItems="False">

使用以下代码：

 public void functionForSelectedValue(int id)
{
    using (SqlConnection con = new SqlConnection(WebConfigurationManager.ConnectionStrings["Molecular"].ConnectionString))
    {
        con.Open();
        using (SqlCommand st = new SqlCommand(@"SELECT    * 
                         FROM       Sample
                         WHERE
                         SampleID=@SampleID", con))
        {

            st.Parameters.AddWithValue("@SampleID", id);

            using (SqlDataReader reader = st.ExecuteReader())
            {
                while (reader.Read())
                {

                    txtUpdateSampleID.Text = reader["SampleID"].ToString();
                    txtUpdateSampleType.Text = reader["SampleType"].ToString();
                    txtUpdateSampleDate.Text = reader["SampleDate"].ToString();
                    txtUpdateSampleTrial.Text = reader["SampleTrial"].ToString();
                    DropDownListUpdateFirstSample.SelectedItem.Value = reader["FirstSample"].ToString();
                    txtUpdateSampleComments.Text = reader["Comments"].ToString();
                    txtUpdateSampleConsultant.Text = reader["ConsultantName"].ToString();
                    DropDownListUpdate.SelectedItem.Value = reader["Diagnosis"].ToString();
                    DropDownListUpdateConsentConfirm.SelectedItem.Value = reader["ConsentConfirmed"].ToString();
                    txtUpdateConsentDate.Text = reader["DateConsent"].ToString();
                    txtUpdateOrther.Text = reader["OtherConsent"].ToString();
                    DropDownListUpdateSectionDecline.SelectedItem.Value = reader["SectionDecline"].ToString();
                    DropDownListUpdateQuarantine.SelectedItem.Value = reader["Quarantine"].ToString();
                    DropDownListUpdateClinicalArchive.SelectedItem.Value = reader["ClinicalArchive"].ToString();
                    DropDownListUpdateResearch.SelectedItem.Value = reader["Research"].ToString();
                    //DropDownListUpdateClinicalArchive.SelectedItem.Value= reader["Research"].ToString();

                }
            }
        }
        con.Close();
    }

}
protected void DropDownListUpdateSample_SelectedIndexChanged(object sender, EventArgs e)
{
    functionForSelectedValue(DropDownListUpdateSample.SelectedItem.Value);
}

和在页面加载中：

召唤

---

希望这能解决您的问题。

加载页面时不会调用

selectedindexchanged

事件绑定数据源

dropdownlist后应设置
SelectedValue
。SelectedValue=youValue感谢您的支持help@EricMbiada，如果它解决了您的问题，请接受答案。
 public void functionForSelectedValue(int id)
{
    using (SqlConnection con = new SqlConnection(WebConfigurationManager.ConnectionStrings["Molecular"].ConnectionString))
    {
        con.Open();
        using (SqlCommand st = new SqlCommand(@"SELECT    * 
                         FROM       Sample
                         WHERE
                         SampleID=@SampleID", con))
        {

            st.Parameters.AddWithValue("@SampleID", id);

            using (SqlDataReader reader = st.ExecuteReader())
            {
                while (reader.Read())
                {

                    txtUpdateSampleID.Text = reader["SampleID"].ToString();
                    txtUpdateSampleType.Text = reader["SampleType"].ToString();
                    txtUpdateSampleDate.Text = reader["SampleDate"].ToString();
                    txtUpdateSampleTrial.Text = reader["SampleTrial"].ToString();
                    DropDownListUpdateFirstSample.SelectedItem.Value = reader["FirstSample"].ToString();
                    txtUpdateSampleComments.Text = reader["Comments"].ToString();
                    txtUpdateSampleConsultant.Text = reader["ConsultantName"].ToString();
                    DropDownListUpdate.SelectedItem.Value = reader["Diagnosis"].ToString();
                    DropDownListUpdateConsentConfirm.SelectedItem.Value = reader["ConsentConfirmed"].ToString();
                    txtUpdateConsentDate.Text = reader["DateConsent"].ToString();
                    txtUpdateOrther.Text = reader["OtherConsent"].ToString();
                    DropDownListUpdateSectionDecline.SelectedItem.Value = reader["SectionDecline"].ToString();
                    DropDownListUpdateQuarantine.SelectedItem.Value = reader["Quarantine"].ToString();
                    DropDownListUpdateClinicalArchive.SelectedItem.Value = reader["ClinicalArchive"].ToString();
                    DropDownListUpdateResearch.SelectedItem.Value = reader["Research"].ToString();
                    //DropDownListUpdateClinicalArchive.SelectedItem.Value= reader["Research"].ToString();

                }
            }
        }
        con.Close();
    }

}
protected void DropDownListUpdateSample_SelectedIndexChanged(object sender, EventArgs e)
{
    functionForSelectedValue(DropDownListUpdateSample.SelectedItem.Value);
}

foreach (DataRow tempRow_Variable in myDataTable.Rows)
     {
        var tempRow = tempRow_Variable;
        DropDownListUpdateSample.Items.Add(tempRow["SampleID"].ToString());

    }
DropDownListUpdateSample.Items.FindByValue("IdforWhichYouWantTobindIt").Selected = true;
functionForSelectedValue(DropDownListUpdateSample.SelectedItem.Value);